A minimax theorem for vector-valued functions in lexicographic order

In this paper, a minimax theorem and a saddle point theorem are obtained for vector-valued functions in the sense of lexicographic order, respectively. An equivalent relationship between the minimax inequality and the saddle point is established. Some examples are given to illustrate our results.     

Applying numerical continuation to the parameter dependence of solutions of the Schrödinger equation

In molecular reactions at the microscopic level, the appearance of resonances has an important influence on the reactivity. It is important to predict when a bound state transitions into a resonance and how these transitions depend on various system parameters such as internuclear distances. The dynamics of such systems are described by the time-independent Schrödinger equation and the resonances are modeled by poles of the S-matrix.Using numerical continuation methods and bifurcation theory, techniques which find their roots in the study of dynamical systems, we are able to develop efficient and robust methods to study the transitions of bound states into resonances. By applying Keller’s Pseudo-Arclength continuation, we can minimize the numerical complexity of our algorithm. As continuation methods generally assume smooth and well-behaving functions and the S-matrix is neither, special care has been taken to ensure accurate results.We have successfully applied our approach in a number of model problems involving the radial Schrödinger equation.     

Letter to the Editor: A note on the preconditioned Gauss-Seidel (GS) method for linear systems

Wen Li (J. Comput. Appl. Math., 182 (2005) 81-90) asserted that there are some errors in article by Hiroshi Niki, Kyouji Harada, Munenori Morimoto and Michio Sakakihara (J. Comput. Appl. Math., 164-165 (2004) 587-600). And Li presented a new proof for the corresponding results in H. Niki et al. In this paper, we point out some errors in Li’s assertion. Moreover, we show that a new proof presented by Li is imperfect.     

基于ASP．NET的在线考试系统设计与实现

随着互联网的普及,越来越多的学校采用在线考试的形式,利用网络进行无软盘、无纸化的在线考试,大大提高了考试的可靠性、有效性、降低了考试成本。在ASP.NET技术和SQL Server 2005数据库系统的基础上,设计和实现基于ASP.NET的四层体系结构的在线考试系统,并实现动态随机组卷和在线阅卷等主要功能,在实际应用中效果良好。     

移动互联的未来——解读Mobile 2．0

Web 2.0的概念和应用已经广泛渗透到我们的生活中,与此同时,随着无线通信的发展和移动终端的普及,Mobile 2.0渐入人们的视野并日益引起广泛关注。在Mobile 2.0时代,移动产业封闭垄断将被打破,用户角色也由信息的消费者转变成为信息的创造者,开放性和以用户为核心将是这个时代移动互联网的基本特征。文章首先介绍了Mobile 2.0概念以及它的产生和发展,阐述了对Mobile 2.0内涵的理解,并详细分析了Mobile2.0理念下移动互联的发展趋势,最后,总结了普及Mobile 2.0应用的障碍,并展望了发展前景。     

Ultrafast laser-driven magnetic-switching scenario in NiO: Role of phonons

We present a fully ab initio ultrafast magnetooptical-switching mechanism in NiO. After obtaining all intragap d-character states of the bulk and the (001) surface with the use of highly correlational quantum chemistry we propagate in time under the influence of a static magnetic field and a laser pulse. We find that switching can be best achieved in a subpicosecond regime with linearly polarized light. The electric-dipole approximation suffices for the surface, however, for the centrosymmetric bulk the presence of an optical phonon is used as a symmetry-lowering mechanism. Lattice (contrary to electronic) temperature is found to enhance the process.     

Simulation of a spintronic transistor: A study of its performance

We study theoretically the magnetic bipolar transistor, and compare its performance with common bipolar transistor. We present not only the simulation results for the characteristic curves, but also other relevant parameters related with its performance, such as: the current amplification factor, the open-loop gain, the hybrid parameters and the cutoff frequency. We noted that the spin-charge coupling introduces new phenomena that enrich the functionality characteristics of the magnetic bipolar transistor. Among other things, it has an adjustable band structure, which may be modified during the device operation; it exhibits the already known spin-voltaic effect. On the other hand, we observed that it is necessary a large g-factor to analyze the influence of the field B over the transistor. Nevertheless, we consider the magnetic bipolar transistor as a promising device for spintronic applications.     

Specific heat of EuIn2P2 at high magnetic fields

We have carried out specific heat measurements on EuIn₂P₂ at high magnetic fields perpendicular to the c-axis in the hexagonal crystal structure in order to understand its thermal properties. The temperature dependence of the specific heat exhibits a clear λ-type anomaly due to a magnetic transition at , indicating that the magnetic transition is of second-order. The λ-type anomaly becomes markedly broader with increasing the magnetic field. This remarkable field-dependence is consistent with the results of previous magnetization measurements which suggest that Eu²⁺ magnetic moments align ferromagnetically perpendicular to the c-axis below T_C. In addition, a hump in the specific heat is observed around 7 K, which can be ascribed to the Zeeman splitting of the Eu²⁺ multiplet by internal magnetic fields.     

The bias- and temperature-dependent electron transport in a magnetic nanostructure

In this paper, we theoretically investigate the effect of the bias and temperature on the electron transport properties in a magnetic nanostructure. It is found that the large spin-polarization can be achieved in such a nanostructure, and the degree of spin-polarization obviously increases with increasing applied bias. It is also found that the conductance curves for the different temperatures obviously intersect at the same Fermi energy for the low Fermi energy, and the degree of spin-polarization decreases with the increase of temperature. Thus, we can control the electron transport through changing the bias and temperature.